I want to build some speakers w/ parts I've got, and need woofers to pair w/ ff85k's (older ones). I think this is what people are calling "fast" speakers, but I don't want the woofer to be powered.
I've got some old 3 way cabinets w/ very cheap woofers, and want to replace them. (all the other drivers in the cabinets are broken/not being used) I'm thinking I could use the 85k's as the mids & highs, cross over at 350ish hz probably first order.
I've read threads that are very similar to what I want to do, full of driver recommendations, but all are for smaller 6-8inch drivers for the lows. Can anyone recommend 12" woofers, or at least point me in the correct direction as to what parameters I should be looking for? I'll be completely honest, some day I want to build the perfect speakers, but don't have a lot of time for research right now. I threw these together today w/ the very cheap woofers that are in the cabinets w.out a crossover, and they sound surprisingly good. I think I can get something pretty well together w/out a ton of effort.
Cabinets are 11x15x27 w/ a front port.

I realize this is the sort of broad question that doesn't always get answered, but it's worth a try Thanks for any help.
maybe I should mention, the amps are 70ish watt push pull tubes.

Given that i have a number of vintage Foster 12" that suit the task that is what i would use personally. They were XOed to a Foster 38mm dome at ~3.5k so they have the extension i like at the top, and we have used the same as woofers for a sub for a client.

The point with a FAST is not to chuck shedloads of money at the bass
unit compared to the mid treble, and with a passive x/o (first order
series is the place to start), the important thing as well as a decent
bass alignment is a higher senstivity for BSC so you don't need to
L-pad the mid treble that much (if at all).

The world of 12" drivers is a murky one at the budget end, but the
point of the bass unit in a FAST is to improve the FR driver, not be
the point of the design.

You've got about 2 cuft and want a driver about 92dB,
a few dB, say 3 to 4 above the FR to be mated with.

If you have space for a very large cabinet and are budget limited, consider the eminence alpha 12a. I've used the alpha 8a and really like it. Even for bass. Sealed I get great bass out of the 8. The 12 would be even better.

Given that i have a number of vintage Foster 12" that suit the task that is what i would use personally. They were XOed to a Foster 38mm dome at ~3.5k so they have the extension i like at the top, and we have used the same as woofers for a sub for a client.

If i had to look to something new, i'd look for similar.

I even have a sketch for a FAST with these woofers.

dave

What's the loading for the Foster 12" in your FAST?

Here's what my pair ended-up like, now in heavily stuffed 50L boxes in a friend's basement.

Sounds about right. Qtc is on the high side in my 50L (1.77 ft^3) box, even with heavy stuffing, but it's perfect for a party speaker. Enough leakage to bring it down to the 0.7-0.8 range might be the ticket for hi-fi.

Thanks everyone. My budget isn't super tight.. I can spend up to about $200 a piece for them.. I'm not out to waste money, either or go all top of the line just for the sake of it. I've got some money to use at Madisound, so have been looking at their woofers, but I don't need to purchase from them.. (they don't have the alphas)

I always see the eminence Alpha's recommended. Why not the Beta's or Delta's? They look like better models, but I have a lot to learn about speakers and right now I don't understand many of the parameters.
I've got a lot of reading to do. Maybe a quick and simple DIY is an impossible task ,